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COMPANY TECHNICAL STANDARD
OFFSHORE PLATFORM HELIDECK DESIGN
07605.ENG.MET.STD
Rev.03 - December 2011
Previous identification code
07605.VAR.OFF.SDS
Rev.03 – December 2011
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ENGINEERING COMPANY STANDARD
Documento riservato di proprietà di Eni spa. Esso non sarà mostrato a terzi né utilizzato per scopi diversi da quelli per i quali è stato inviato.
This document is property of Eni spa. It shall neither be shown to third parties nor used for purposes other than those for which it has been sent.
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COMPANY SPECIFICATION
OFFSHORE PLATFORM
HELIDECK DESIGN
07605.VAR.OFF.SDS
Rev.3 December 2011
3
REV.
General revision
DESCRIPTION
TEOF
TEOF
MONACO
12/2011
COMPILED
VERIFIED
APPROVED
DATE
ENGINEERING COMPANY STANDARD
This document is property of Eni S.p.A. Exploration & Production Division.
It shall neither be shown to Third Parties not used for purposes other than those for which it has been sent.
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Rev.3 December 2011
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FOREWORD
Rev. 3
No. of sheets 12
December 2011
Review to comply with the ICAO normative and updating of the general criteria for the
design of offshore platforms helideck considering the Eni Standard (Aviation Manual).
Change code from SPC to SDS (company specification).
Rev. 3 is issued in English language only.
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INDEX
1.
PURPOSE AND USE ....................................................................................................... 4
2.
2.1
2.2
2.3
REFERENCE RULES AND DEFINITIONS...................................................................... 5
NORMATIVE AND RULES ............................................................................................... 5
ENI STANDARD ............................................................................................................... 5
DEFINITIONS ................................................................................................................... 5
3.
3.1
3.1.1
3.1.2
CHARACTERISTICS OF MAIN TYPE OF HELICOPTERS ............................................ 6
GENERAL ......................................................................................................................... 6
OPERATIONS IN ITALY................................................................................................... 6
OPERATIONS ABROAD .................................................................................................. 6
4.
CHOICE OF THE HELIDECK LOCATION AND OPERATION ....................................... 7
5.
5.1
5.2
5.2.1
5.2.2
GEOMETRIC AND STRUCTURAL DIMENSIONING...................................................... 8
GEOMETRICAL CHARACTERISTICS............................................................................. 8
STRUCTURAL DIMENSIONING ...................................................................................... 8
GENERAL ......................................................................................................................... 8
TYPICAL DIMENSIONING ............................................................................................... 8
6.
6.1
6.2
6.2.1
6.2.2
6.3
STRUCTURAL DESIGN................................................................................................... 9
GENERAL ......................................................................................................................... 9
DESIGN ACTIONS ........................................................................................................... 9
HELICOPTERS LANDING................................................................................................ 9
HELICOPTERS AT REST .............................................................................................. 10
LOAD COMBINATIONS ................................................................................................. 11
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1.
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PURPOSE AND USE
This specification describes Eni requirements and characteristics to be applied in the design of
offshore helidecks and it shall be read in conjunction with the other Eni standards refer to helideck
design as indicated in § 2.2.
Construction indications are provided aimed at ensuring the availability of helidecks with the desired
operational and safety characteristics.
The following is a description of helidecks for fixed or floating platforms. Helideck structures should
be designed in accordance with ICAO requirements (the Heliport Manual), relevant International
Standards Organization (ISO) codes for offshore structures and, for a floating installation, the
relevant International Maritime Organization (IMO) code.
The specific requirements relating to the latter are usually considered separately, through explicit
notes or references, as the main requirements refer to fixed platforms.
This specification is therefore used to define the characteristics intended for helidecks in the Tender
Documents necessary for:
ƒ
ƒ
Structural basic design;
Turn key contracts for accommodation and helidecks including engineering activities.
The maximum size and mass of helicopter for which the helideck has been designed should be
stated in the Installation/Vessel Operations Manual and Verification and/or Classification document.
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2.
2.1
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REFERENCE RULES AND DEFINITIONS
NORMATIVE AND RULES
[1]
ICAO (International Civil Aviation Organisation) - Aerodromes Annex 14 to Convention on
International Civil Aviation” - VoI. II Heliports – 3rd Edition July 2009.
[2]
ICAO (International Civil Aviation Organisation) - "Heliport Manual" Doc. 9261 - AN/903/2 - II
Edition (1985).
[3]
ISO 19901-3 Petroleum and natural gas industries – Specific requirements for offshore
structures – Part 3:Topsides Structures
[4]
Civil Aviation Authority – CAP437 Offshore helicopter landing areas: guidance on
standards April 2010.
[5]
IMO (International Maritime Organisation) Code for the Construction and Equipment of
Mobile Offshore Drilling Units
2.2
[6]
2.3
ENI STANDARD
AVIATION MANUAL - SELT.DG.0237.08
DEFINITIONS
Helideck
An area located on a floating or fixed structure offshore designated for use by helicopters.
For each helideck specific areas are determined for Approach and Take-Off and for Touchdown and
Lift-off, in addition to all the auxiliary systems and equipment needed for a safe conduction of flight
procedures and adequate protection of all personnel.
ICAO
International Civil Aviation Organization
F.A.T.O (Final Approach and Take-off Area)
A defined area over which the final phase of the approach manoeuvre to hover or land is
completed, and from which the take-off manoeuvre is commenced.
MTOM
Maximum Take-Off Mass
Landing Area
A generic term referring to any area primarily intended for the landing or take-off of aircraft.
D-Value
The largest overall dimension of the helicopter when rotors are turning. This dimension will normally
be measured from the most forward position of the main rotor tip path plane to the most rearward
position of the tail rotor tip path plane (or the most rearward extension of the fuselage in the case of
Fenestron or Notar tails).
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3.
CHARACTERISTICS OF MAIN TYPE OF HELICOPTERS
3.1
GENERAL
The main geometrical and weight characteristics of helicopters (design) used in the offshore
operations are reported in Reference [6].
Without particular indications about the reference helicopter, to guarantee the operability of a large
range of helicopters the standard values for the dimensions D-value and weight (MTOM) are
reported in the Table 1.
Category
D-value [m]
MTOM [kg]
Structure type A
Up to medium size
18.00
7.000
Structure type B
Heavy size
22.00
13.000
Table 1 – Standard values for helideck design
The category reference and relative structure type shall be choice in function of the distance
between the offshore structure and the shore, as following indicated:
ƒ
Offshore structure quite near shore < 40 nm (nautical miles)
ƒ
Offshore structure far to shore > 40 nm (nautical miles)
3.1.1
Operations in Italy
For the Italy purpose, if the particular helicopter is not request, it’s suggested to refer to “structures
type A” in the table above.
3.1.2
Operations abroad
For plants abroad the helicopters to use in each case will be verified. Refer to Table 1 if the specific
helicopter is not request.
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4.
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CHOICE OF THE HELIDECK LOCATION AND OPERATION
As far as the helideck's optimum position is concerned, within a certain platform layout, reference is
also made to ENI specification Reference [6]
In general, the following aspects shall be particularly verified:
a) In accordance with point b) it is preferable that the helideck is not above the maximum of 60
m from the average sea level.
b) When the helideck is placed directly on the other structures is liable to suffer from excessive
vertical airflow components unless there is sufficient separation to allow airflow beneath the
helideck. To avoid this problem when the helideck is over other structures, enough space
must be provided in between them to allow airflow below the helideck itself.
c) The approach and take-off directions of the helideck shall be free of objects.
d) The helideck shall have approach and departure directions opposed to the direction of
prevailing winds, which is situated downwind; generally, this is against the platform safety
prescriptions, requiring a L. Q. situated upwind with respect to wells, flares, process areas.
A compromise shall be found for the orientation, with the methods indicated in the above
mentioned specification.
For this purpose, it must be noted that, during take-off and landing operations, the maximum
transversal speed oft he wind is 20 Knots.
e) The helideck location shall be as far as possible from turbulent emission areas or with a
different temperature from the average air temperature. Drains, chimneys, flares shall
therefore be considered to verify that arrival or departure directions of the helicopter do not
require flying over.
f)
The helideck shall be accessible from the L.Q. at least through two ramps spaced 180° each
other plus one emergency exit, positioned between.
g) The internal edge of the helideck shall be easily reached with at least one of the cranes, to
move items with a minimum weight of 1 ton.
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5.
GEOMETRIC AND STRUCTURAL DIMENSIONING
5.1
GEOMETRICAL CHARACTERISTICS
The dimensions of the helideck shall be defined in compliance with the dimensions of the largest
helicopter foreseen to land on the structure.
In detail, the helideck will have a geometrical configuration such to contain a circumference with a
diameter D such that
ƒ
D = O.L (Overall Helicopter Length)
ƒ
D = 0.9 O.L. (Overall Helicopter Length) for double rotor helicopter
for single rotor helicopter
In case of the specific helicopter are not defined refer a D-value as indicated in the § 3.1.
5.2
STRUCTURAL DIMENSIONING
5.2.1
General
The structures constituting the helideck framework are:
ƒ
Plates
ƒ
Plane stiffeners
ƒ
Support structures
The dimensioning of these elements shall be done with refer to the ICAO normative as indicated in
the following chapters and foreseen in the latest edition of the normative.
5.2.2
Typical Dimensioning
In the absence of particular requirements, the following dimensioning, relevant to helidecks for
standard Living Quarters, and based on the helicopters indicated in § 3.1, shall be assumed as the
work basis for the verification:
1.
PLATES
Thickness
Field (max.)
Material
8.5mm
4,000 x 400 mm
Fe 510 B
2.
STIFFENERS
Thickness
Type
Material
400 mm
IPE 140
Fe 430 B
3.
STIFFENERS
Interasse (max)
Type
Material
4000 mm
IPE 400
Fe 430 B
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6.
STRUCTURAL DESIGN
6.1
GENERAL
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The FATO area must be designed to accommodate the largest and heaviest helicopter expected to
use the helideck; furthermore other factors must be taken into account like the loading of personnel,
freight, snow, refuelling equipment, etc.
For single-main-rotor helicopters, the total actions imposed on the structure are normally taken as
concentrated actions at the undercarriage centres of the specified helicopter and divided equally
between the two main undercarriages.
For tandem-main-rotor helicopters, these actions are normally taken as concentrated actions at the
undercarriage centres of the specified helicopter and distributed between the main undercarriages in
the proportion in which they carry the maximum static action.
These concentrated undercarriage actions are normally treated as point loads; alternatively, a tyre
contact area can be assumed in accordance with the manufacturer's specification. The maximum
take-off mass and undercarriage centres of the helicopter for which the helideck has been designed
should be documented.
Plastic design considerations may be applied to the deck (i.e. plating and stiffeners) but elastic
design shall be used for the main supporting members (girders, trusses, pillars, columns, etc.) so as
to limit deflections and reduce the likelihood of the helideck structure being so damaged as to prevent
other helicopters from landing.
Characteristics of the FATO area (therefore also the Touchdown and Lift-Off area) must take into
account the worse situation deriving from a consideration of the following two circumstances; one
dynamic, the other static.
6.2
DESIGN ACTIONS
6.2.1
Helicopters Landing
The helideck shall be designed to withstand all the forces likely to act when a helicopter lands
including:
a)
Dynamic load due to impact landing
This will cover both a normal landing and an emergency landing.
For the former, an impact load of 1.5 x maximum take-off mass (MTOM) of the helicopter is
used, which equates to the serviceability limit state. This will be treated as an imposed load,
distributed as described in the section 6.1 and applied together with the combined effect of b) to
f) below in any position on the safe landing area so as to produce the most severe landing
condition for each element concerned.
For an emergency landing, an impact load of 2.5 x MTOM, which equates to the ultimate limit
state, shall be applied as described in the section 6.1 in any position on the landing area
together with the combined effects of b) to f) inclusive.
b)
Sympathetic response of landing platform
The dynamic load (see a) above) shall be increased by a structural response factor depending
upon the natural frequency of the helideck structure. It is recommended that a structure
response factor of 1.3 is used unless further information is available to allow a lower factor to be
calculated. Information required to do this will include the natural periods of vibration of the
helideck and dynamic characteristics of the designated helicopter and its landing gear.
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Overall superimposed load on the landing platform
2
To allow for snow, personnel etc. in addition to wheel loads, an allowance of 0.5 kN m shall
be added over the whole area of the helideck.
d)
Lateral load on landing platform supports
The landing platform and its supports must be designed to resist concentrated horizontal
imposed loads equivalent to 0.5 x maximum take-off mass of the helicopter, distributed between
the undercarriages in proportion to the applied vertical loading in the direction which will produce
the most severe loading on the element being considered.
e)
Dead load of structural members
f)
Wind loading
Wind loading shall be allowed for in the design of the platform. This is applied in the direction
which, together with the imposed lateral loading, will produce the most severe loading condition
on each element.
g)
Punching shear
A check must be made for the punching shear from an undercarriage wheel with a contact area
3
2
of 64.5 x10 mm acting in any probable location. Particular attention to detailing shall be taken
at the junction of the supports and the deck.
6.2.2
Helicopters at Rest
The helideck shall be designed to withstand all the applied forces that could result from a helicopter
at rest; the following needs to be taken into account:
a)
Imposed load from helicopter at rest
The helideck shall be designed to resist an imposed load equal to the maximum take-off mass of
the helicopter. This load will be distributed between the two main wheels or skids of the
helicopter. It shall be applied in any position on the helicopter platform so as to produce the
most severe loading condition for each element considered.
b)
Overall superimposed load, dead load and wind load
The values for these loads are considered to act in combination with a) above (see the
superimposed load in the Tab.2). Consideration shall also be given to the additional wind
loading from any parked or secured helicopter.
c)
The effect of acceleration forces and other dynamic
Amplification forces arising from the predicted motions of mobile installations and vessels, in the
appropriate environmental conditions corresponding to a 10-year return period, shall be
considered.
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The values of the overall superimposed load on landing platform are shown in the table below.
Superimposed
Load
Maximum take-off weight
LH
Undercarriages
wheel
centres
Superimposed
Load
(Case A)
Superimposed
Load
(Case B)
[kg]
[kN]
[m[
(SHa)
[kN/m²]
(SHb)
[kN/m²]
1
Up to 2,300
Up to 22.6
1.75
0.5
1.5
2
2,301 – 5,000
22.6 – 49.2
2.5
0.5
2.0
3
5,001 – 9,000
49.2 – 88.5
2.5
0.5
2.5
4
9,001 – 13,500
88.5 – 133.0
3.0
0.5
3.0
5
13,501 – 19,500
133.0 – 192.0
3.5
0.5
3.0
6
19,501 – 27,000
192.0 – 266.0
4.5
0.5
3.0
Table 2 – Overall superimposed load
6.3
LOAD COMBINATIONS
In the Table 3 and 4 are summarized the design loads and the partial load factors
Table 3 - Load Combination for Emergency Landing
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Table 4 – Load Combination for helicopter at rest